1. Field of the Invention
This invention relates to cartridge fuses and in particular to a terminal adapter accommodating the installation of cartridge fuses in a variety of fuse holders.
2. Description of the Prior Art
The prior art includes a number of terminal adapters for securing cartridge fuses in a variety of fuse holders as well as rejection type fuse holders designed to insure the installation of the proper class of fuse in a particular application.
The terminal adapters shown in U.S. Pat. Nos. 2,889,533 and 4,128,291 are fairly typical of the adapters heretofore in use. For example, U.S. Pat. No. 2,889,533 shows a clip-type fuse holder incorporating an adapter accommodating the installation of a fuse having either ferrule or knife-blade type terminals. Similarly, U.S. Pat. No. 4,128,291 shows a clip-type fuse holder having an adapter accommodating the installation of fuses having different size ferrule terminals.
While the foregoing arrangements have been for the most part satisfactory, providing a structure which maintains adequate contact between the fuse terminals and the fuse holder to prevent overheating due to high resistance in the joints between those members has continued to be an area of concern. This is particularly the case with clip-type fuse holders where the terminals of the fuses are typically wedged between the cantilevered legs of the U-shaped fuse holders. Thus, proper sizing of the fuse terminals for a particular fuse holder is important to insure the integrity of the electrical connection between those members.
In addition to the above, the prior art also includes a number of rejection type fuse holders which have been used to prevent the installation of the wrong class of fuse in a particular application. Fuse holders of this type have been necessary since many cartridge fuses are the same size and current rating but have different current interrupting capacities. For example, a current limiting, high interrupting capacity, class R cartridge fuse is essentially the same size as a non-current limiting, low interrupting capacity, class H fuse.
Obviously, since the current limiting, class R fuse incorporates the additional protective feature of extremely fast operation to prevent the flow of extremely high currents as compared to a non-current limiting fuse, a potentially hazardous situation could result if a class H fuse was inadvertantly substituted for a class R fuse. Consequently, it has generally been required to incorporate some means in the fuse holder to prevent the replacement of the current limiting fuse with a non-current-limiting fuse. U.S. Pat. Nos. 4,099,828 and 4,108,531 show two rejection fuse holders which were designed to secure class R cartridge fuses having ferrule and knife-blade terminals, respectively. In both cases, one terminal on each of the fuses is provided with a notch or groove keyed to the rejection fuse holder which accepts the keyed terminal of the class R fuse but does not accept the unkeyed terminal of a class H fuse.